It is known to assign a separate engine-brake valve in an internal combustion engine in addition to the exhaust valves, which engine-brake valve will be actuated in a cyclic manner or will be open permanently. Such engine-brake valves are usually actuated hydraulically or pneumatically and are known for example from DE 44 23 657 C2, DE 38 39 452 C2, DE 38 39 450 C2, AT 004.387 U1 or AT 003.600 U1. An engine-brake device is further known from DE 41 25 831 A1, the engine-brake valve of which can be actuated electrically.
Known actuating devices for engine-brake valves require a relatively high constructional effort and require a comparatively large amount of space in the cylinder head, which can be provided only with difficulty in many cases. In order to depressurize the cylinder pressure, an additional container and a high-pressure oil system with a high-pressure pump and electrohydraulic valves are required for each cylinder. Furthermore, known engine-brake devices comprise a large number of individual parts which increase the susceptibility to malfunctions and have a disadvantageous effect on the production process.
DE 39 36 808 A1 describes an exhaust-cam-controlled engine brake for four-stroke internal combustion engines, in which the exhaust control is advanced by approximately one working stroke, i.e. a crank angle of approx. 180°, for the duration of the required braking effect. This leads to a doubling of the braking cycles and a decompression at the end of the compression stroke, by means of which a higher sustained-action braking effect can be achieved.
U.S. Pat. No. 6,000,374 A describes an engine brake for an internal combustion engine in which several braking phases can be realized per working cycle. An additional brake rocker arm is provided per cylinder in addition to the intake and exhaust rocker arms, said additional brake rocker arm, which is driven by a brake cam, actuating an exhaust valve. All rocker arms comprise a hydraulic element at its valve-side end. Solenoids can influence which hydraulic elements will be subjected to compressed oil and which will not. It is ensured in this manner that in normal working operation the brake rocker arm will only run empty and the exhaust valve will not be actuated by the brake rocker arm because its hydraulic element is unable to transmit the force without oil supply. The intake and exhaust rocker arms will operate in working operation as long as their hydraulic elements are filled with oil. The hydraulic elements of the exhaust rocker arms will be deactivated in braking operation and the hydraulic elements of the brake rocker arms will be activated. This also allows hydraulically manipulating the valve movements in order to ensure brake power control and adjustment to each rotational speed. It is disadvantageous that a high control input is required.
An engine braking device for an internal combustion engine is known from JP 05-33684 A, which comprises two exhaust valves per cylinder, said exhaust valves being actuated in driving operation via a valve bridge by an exhaust cam and an exhaust valve lever. A divided brake lever is arranged adjacent to the exhaust valve lever, the two parts of which are rotatably mounted about the valve lever axis independent of one another. A brake cam acts on the brake valve lever part on the camshaft side. The brake lever part on the valve side acts on the valve shaft of one of the two exhaust valves. The two brake valve lever parts are rotationally connected with each other in engine braking operation via a locking device, so that the elevation of the brake cam will be transmitted via the brake lever onto the one exhaust valve. Only simple braking phases can be realized with this mechanism.
Similar engine brake devices with levers or lever parts which can be connected with each other by a locking element are known from the publications EP 1 113 151 A2, EP 0 826 867 A1, JP 2004 084 596 A, EP 0 420 159 A1, U.S. Pat. No. 5,809,952 A, JP 01-003 210 A or EP 0 588 336 A1. It is a common aspect in all these devices that they are not suitable for a dual-phase braking effect.